In geometric measure theory, Falconer's conjecture, named after Kenneth Falconer, is an unsolved problem concerning the sets of Euclidean distances between points in compact d {\displaystyle d} -dimensional spaces. Intuitively, it states that a set of points that is large in its Hausdorff dimension must determine a set of distances that is large in measure. More precisely, if S {\displaystyle S} is a compact set of points in d {\displaystyle d} -dimensional Euclidean space whose Hausdorff dimension is strictly greater than d / 2 {\displaystyle d/2} , then the conjecture states that the set of distances between pairs of points in S {\displaystyle S} must have nonzero Lebesgue measure.